unit 8

计算机网络基础，整理有： 1.What is a computer network 2.Components of Computer Network 3.Uses of Computer Network 4.Computer Network Architecture...

Computer Network Basic

• 1.What is a computer network
  • computers connected with each other through wires, can interact with each other through a network, to share resources among various devices.
• 2.Components of Computer Network
  • NIC
    • helps the computer to communicate with another device.
    • two types
      • Wireless NIC
        • All the modern laptops use the wireless NIC. that employs the radio wave technology.
      • Wired NIC
        • Cables use the wired NIC to transfer the data over the medium.
  • Hub
    • central device that splits the network connection into multiple devices.
  • Switch
    • networking device that groups all the devices over the network to transfer the data to another device.
  • Cable
    • transmission media that transmits the communication signals.
    • Twisted pair cable: high-speed cable that transmits the data over 1Gbps or more.
    • Coaxial cable: like a TV installation cable. It is more expensive than twisted pair cable, but it provides the high data transmission speed.
    • Fibre optic cable: It is a high-speed cable that transmits the data using light beams. It provides higher data transmission speed as compared to other cables. It is more expensive as compared to other cables.
  • Router
    • a device that connects the LAN to the internet. The router is mainly used to connect the distinct networks or connect the internet to multiple computers.
• 3.Uses of Computer Network
  • Resource sharing:
    • the sharing of resources such as programs, printers, and data among the users on the network without the requirement of the physical location of the resource and user.
  • Server-Client model:
    • A server is a central computer used to store the information and maintained by the system admin- istrator. Clients are the machines used to access the information stored in the server remotely.
  • Communication medium:
    • Computer network behaves as a communication medium among the users.
  • commerce:
    • People can do business over the internet.
• 4.Computer Network Architecture
  • defined as the physical and logical design of the software,hardware, protocols, and media of the transmission of data.
  • Peer-to-Peer Network
    • is a network, useful for small environments, usually up to 10 computers. no dedicated server.
    • Advantages
      • does not contain any dedicated server. less costly
      • each computer manages itself. easy to set up and maintain
    • Disadvantages
      • does not contain the centralized system. cannot back up the data as the data is different in different locations.
      • has a security issue as the device
  • Client/Server Network
    • model designed for the end users called clients，A server performs all the major operations such as security and network management.
    • Advantages
      • can back up the data easily.
      • improves the overall performance of the whole system.
      • Security is better in client/server network
      • increases the speed of the sharing resources.
    • Disadvantages
      • expensive as it requires the server with large memory.
      • the cost of NOS is very high.
      • requires a dedicated network administrator to manage all the resources.
• 5. Features of Computer Network
  • Communication Speed
  • File Sharing
  • Easy Back up
  • Software and Hardware Sharing
  • Security
  • Scalability
  • Reliability
• 6. Computer Network Types
  • LAN (Local Area Network)
    • group of computers connected to each other in a small area
  • MAN (Metropolitan Area Network)
    • covers a larger geographic area by intercon- necting different LANs to form a larger network.
    • Uses
      • communication between the banks in a city.
      • an airline reservation.
      • college within a city.
  • WAN (Wide Area Network)
    • a network that extends over a large geographical area such as states or countries.
    • Examples
      • Mobile broadband
      • Last mile
      • Private network
    • Advantages
      • Geographical area:
      • Centralized data:
      • Get updated files:
      • Exchange messages:
      • Sharing of software and resources:
      • Global business:
    • Disadvantages
      • Security issue
      • Need of firewall and antivirus software
      • High setup cost
      • Troubleshooting problems
  • Internetwork
    • An internetwork is defined as two or more LANs or WANs or computer network segments Which are connected using devices
    • two types
      • extranet：a communication network based on the internet protocol
      • intranet：a private network based on the internet protocol.